Since it is well established that blowouts, subsurface structure damage, costly breakdowns with stuck pipe, and several other undesirable side-effects are directly associated with the drilling fluid (mud) circulation system in drilling a well, a method and apparatus for providing essential and accurate fluid systems data will be of great use and service to the industry and the art. By the very nature of drilling fluids, (drilling mud) as is well known by those familiar with the art, densities are continually changing, foreign materials and particles are constantly introduced into the system, and those fluid measuring devices presently in use have moving parts which are designed to come into actual physical contact with the drilling fluids during their operation. For example, fluid pit floats, which measure pit levels must float on the drilling fluids to operate and frequently they indicate different levels merely on change of fluid densities regardless of actual level changes. Pump stroke counters, which measure piston displacement are accurate only to the degree of pump efficiency and most pumps that have been used in the field for any period of time have varying reduced efficiencies. Flow meters are some times affected by foreign particles and have been known to produce inaccurate results. Volumetric accuracies to minimal tolerances are especially desirable in detecting a so called "kick" (incursion of gases and/or formation fluids down-hole) inasmuch as the rate of gas expansion from bottom hole to surface is exponentially increased so that a volume of one barrel at the bottom of the hole might increase to hundreds of barrels at the surface.
Because of the infinite variety of fluid conditions encountered in drilling a well, it is suggested that those devices presently used for measuring drilling mud volumes, all of which have moving parts coming into contact with the fluid itself, have inherent inaccuracies which at times exceed tolerable parameters, and therefore it is desirable to provide a method and a device which can accomplish the measurement of drilling fluid volume and densities without the necessity of having any moving parts coming into contact with the fluid itself. It is also desirable that drilling fluid volumes can be indicated independent of their densities and conversely that densities can be indicated independently of volume. It is desirable that accuracies of less than one barrel pit volume change and 0.075 lb./gallon mud weight change be achieved in order to fall within tolerable parameters; this method and apparatus as hereinafter described accomplishes these goals.
An object of the present invention is to provide a method and apparatus for monitoring mud measuring drilling fluid (mud) weight in each fluid pit of a fluid drilling system.
Another object of the present invention is to provide a method and apparatus for monitoring and measuring drilling fluid (mud) volume in each fluid pit of a fluid drilling system.
A further object of the present invention is to provide a method and apparatus for totalizing drilling fluid (mud) volume in a plurality of fluid pits together with a 24 hour record of said total volume.
A still further object of the present invention is to accomplish the foregoing objects with no moving parts coming into contact with the drilling fluids which have heretofore caused a margin of error by the mud fouling the moving parts of present measuring devices.
A further object of the present invention is to determine mud depth independent of mud weight.
A further object of the present invention is to determine mud weight independent of mud depth.
A further object of the present invention is to provide an early warning indication by furnishing mud weight and change of depth information in the "possum belly."
A still further object of the present invention is to provide a system having the most accurate measurement with sensitivities exceeding prior art devices addressing themselves to the same problem with a minimum of field calibration.